The prices of goods and services must cover their costs. Costs include labor, materials, and capital.
Capital costs to a borrower include a return to the saver who supplied the capital, plus a mark-up (called a "spread") for the financial intermediary that brings the saver and the borrower together.
The more efficient the financial system, the lower the costs of intermediation, the lower the costs to the borrower, and, hence, the lower the prices of goods and services to consumers.
Financial systems (i.e. financial intermediaries and financial markets) channel funds from those who have savings to those who have more productive uses for them.
They perform two main types of financial service that reduce the costs of moving funds between borrowers and lenders, leading to a more efficient allocation of resources and faster economic growth. These are the provision of liquidity and the transformation of the risk characteristics of assets.
To learn more about financial markets, refer to these sources:
Principles of Finance By Scott Besley, Eugene F. Brigham
Treasury.govt.nz - The role of financial systems in the economy